Process for producing synthetic lumber that is not attacked by molds



Patented Feb. 13, '1934 ,usti

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PROCESS FOR PRODUCING SYNTHETIC LUMBER THAT IS NOT ATTACKED BY MOLDS Orland R. Sweeney, Ames, Iowa, assignor to Iowa State College of Agriculture and Mechanic Arts, Ames, Iowa, a corporation of Eowa No Drawing. Original application May 27, 1929, Serial No. 374,274, now Patent No. 1,803,737, dated May 5, 1931. Divided and this application April 13, 1931. Serial No. 529,884

Claims.

This invention relates to the process or method of treating synthetic lumber, paper or the like against attacks from molds. For purposes of illustration I will specifically consider and herein 5 discuss the treating of synthetic'lumber made from cornstalks against such attacks by molds and the like. To this end the invention may consist of, first; cooking the unshredded corn plant under pressure, second; allowing it to stand 10 for a certain length of time without washing it, third; passing it through a rod mill or like, fourth; suitably washing the same, fifth; passing the washed product through a refining machine, sixth; treating said material with a suitable amount of water, seventh; adding to said mass a sizing material such as rosin or alum, eighth; mixing copper sulphate in the mass, and ninth; forming it into a board and drying it on a suitable machine. When such a board is formed it will be economical in manufacture, durable and strong in use, and will be free from the possibility of its deterioration by molds. The step by step procedure may be varied as will hereinafter be explained.

Heretofore, a great deal of experimenting has been done in attempting to make suitable synthetic lumber from cornstalks and from this standpoint I might state that my United States Letters Patent on a Process relating to the production of synthetic lumber from cornstalks, Patent No. 1,803,737 under date of May 5, 1931, and of which this invention is a division, goes into great detail to explain.

Suffice it to say that the examination of the cornstalk shows that it is composed of a hard outer shell called the cortex. This cortex surrounds a soft pulpy material known as pith or parenchyma, and this pith surrounds elongated cell fibers called vascular bundles. Any processing of this material is difiicult because of the different physical properties. For example, if the grinding machinery is not especially adapted to the purpose, the pith will be beat to a jelly long before pieces of the outside fibers are reduced to a suitable pulp.

This causes the mat forming machine to become clogged and produce an unsatisfactory product. Likewise in the digesting of the comstalks with chemicals, no wholly satisfactory process has been worked out because the pith and vascular bundles are completely hydrolyzed and disintegrated before the cortex is properly cooked.

In the standard practice it is the custom to shred or otherwise comminute the cornstalks before subjecting them to cooking or chemical treatment.

I' have found that if the cornstalks be unshredded and then fed into the digester as they come in bales or directly from the field, before 30 they have been given any serious mutilation, and that if the digestion be carried out using approximately pure water, or in other words water whose pH value does not vary greatly from 7.0, and that if these whole unmutilated stalks are subjected to a pressure of from thirty to one hundred pounds in contact with hot water, that there results a product which when properly macerated gives a board of great strength and of highly desirable properties for use in the arts.

I have also found that it is advisable after cookthe cornstalks for from one to three hours under such a pressure with hot water, that the fibers will be made tougher and that the pith cells will draw into fiber better and'be removed more com- 7 pletely from the fibrous cortex cells if I allow the cooked stalks to standfor from four to twentyfour hours before they are further handled in the processes. This standing has a double advantage in that it allows the fibers to absorb from the cook liquorsligneous or pentosic materials which probably partly oxidize and at the same time the greater amount of the cooking liquors drain away thus reducing thenecessity for excessive washing of the material.

In order to get the best results from the water digested fibers or cornstalks as prepared in the foregoing manner, I next pass the cornstalks through a heavy rod mill. This rod mill is of the usual construction consisting of a large drum mounted for rotation and having a plurality of heavy rods therein.

As the drum revolves on its axis the rods naturally either tumble over each other orrise upon the side of the drum and slide down continuously. It is obvious that if the rods tumble from the top portion of the drum downwardly, a pounding action will result, whereas if the rods slide down the side they will give a rubbing action to the material inside the drum.

For my purposes I prefer the rubbing action as it draws the pith cells into long fibers which do not jell up and which workbetter when commingled with the tough, strong cortex fibers. The obtaining of this result will vary with the difierent types of rod mills, but any skilled workman can easily determine the speed the drum should rotate for realizing this rubbing action. Results will also depend on the rate the cornstalks are fed into the mill. Obviously the larger the rods lid and rod mill the greater the feed must be in order to produce satisfactory fiber.

I have found that it is best to run the cornstalks through at such a rate as to cause the cortex fibers at the discharge end to vary in lengths from very short fibers to fibers of about one-half inch in length. Best results are not generally obtained by attempting to completely reduce the pulp in the rod mill. By passing the cornstalks through at a rate to give fibers of the above-mentioned dimensions, the pith is not excessively jelled, but is drawn into fibers. There will also be produced a small percentage of thread-like fibers several inches in length which is very desirable.

It is necessary to feed into the rod mill at the same time that the stalks are going through, an amount of water such as to make the cornstalk fiber come from the discharge freely. The amount of this water will be at least five hundred per cent of the weight of the cornstalks fed into the mill.

After the pulp has come through the mill it is now coarse enough to be free on a screen which is so positioned as to receive the pulp. It is upon this screen that the cornstalk pulp is washed with water to remove a certain amount of the pentosans and lignins produced during the water cooking. This washing must not be too thorough because the adhesive properties of these beforementioned materials are desirable. If, however, none of the lignins or pentosans are washed out, the board will not be free enough on the machines used to make up the same. The screen should be of approximately forty mesh and may be either of the inclined sheet type or the rotating cylinder type. As the pulp travels down and across the screen it is washed by the water sprayed on it which can be controlled by a valve in the water line.

If a very refined board is desired, the pulp from the washing screen should be passed through a refiner in order to take out the small pieces of material which are sometimes termed shiners or chives. After the pulp is washed, a suitable amount of water is added to the same and to this mass usually is added a sizing material such as rosin or alum. The mass is then conveyed to the board forming machine as is well known in the art.

. The above discussion will give a general idea of one way of making and forming a synthetic lumber and will form a basis upon which I may discuss the treating of the same against molds. Therefore, generally I would state that this invention consists of injecting a substance into the pulped mass that eliminates molds.

Copper sulphate is an excellent poison and may be successfully used by adding to the pulp suspension a few hundredths of a percent of the same, which is absorbed by the fibers. 1 By this method of treating the synthetic lumber, the copper sulphate is thoroughly distributed throughout the board, thereby making it impossible for molds to attack the board either from the outside or inside. However, synthetic lumber as I herein describe provides a situation where the pulp can be treated by copper sulphate and the mold repellent will therefore be completely throughout the synthetic board.

When the pulp is placed on the board forming machine it is pressed in the usual manner by rollers or the like and the water removed from the same. The water thus removed is generally called white waters" and I have found that for economy of water consumption it is desirable to use this water by returning it to the process. I use it direct for washing the pulp and for diluting the pulp in the refining machine.

In "the process where the white waters are used over again it is feasible and practical to continuously feed in the copper sulphate, and since the white waters, which contain the excess copper sulphate, are returned to the process there will be no loss of these materials except as they are absorbed in the board. By such a process as I have explained, i. e., the mixing of a small percent of copper sulphate in the pulp mass, the finished board will be effectively saturated with the copper sulphate.

After the copper sulphate is successfully mixed with the pulp mass it is passed to the usual board forming machine which largely removes the water from the pulp and this pulp which is in the form of a damp mat is passed into a dryer and dried into the desired lumber.

I claim as my invention:

l. The process of manufacturing and producing a synthetic insulating lumber from comstalks consisting in the breaking up of the cornstalks into comparatively fine pieces, commingling the pieces with Water, treating the mass with copper sulphate solution, and then forming the mass into lumber by pressing and drying.

2. The process of manufacturing and producing a synthetic insulating lumber from cornstalks consisting in the cooking of the cornstalks in water, disintegrating the material by a suitable machine, commingling the pieces with water, injecting copper sulphate solution into the disintegrated mass, and last forming the mass into lumber by pressing and drying.

3. The process of manufacturing and producing a synthetic lumber from cornstalks consisting in the cooking of the unshredded corn plant in water under pressure, discharging the material from the cooker, rubbing and breaking the cornstalks into elongated particles by a suitable machine such as a rod mill, treating the particles with water, injecting copper sulphate solution into the mass, and last forming the mass into lumber by pressing and drying.

4. The process of manufacturing and producing a synthetic lumber from cellulosic plant material consisting in the cooking of the plant in water, breaking of the plant material into particles, washing the particles, commingling the particles with water, treating the mass with a sizing material, adding to the mass a copper sulphate solution, forming said mass into a mat on a forming machine, returning the white waters obtained from the forming of the mat back into the process for diluting additional plant material coming through theprocess, and last forming the mass into lumber by pressing and drying.

5. The process of manufacturing and producing synthetic lumber from cornstalks consisting in the breaking of the cornstalks into particles, washing the particles, commingling the particles with water, placing copper sulphate solution into the water, forming the mass into a mat, returning the white waters obtained by forming the mass into a mat back to the process for diluting additional plant material coming through the process, adding copper sulphate to the returned white waters, and last forming the mass into lumber by pressing and drying.

ORLAND R. SWEENEY. 

